2018-03-07

#TESSninja, day 3

My plan for #TESSninja is to work on automated approaches to radial-velocity follow-up of TESS discoveries. I am bringing some new things to this question. The first is that I am not going to ask “when should I next observe this planet candidate?”, I am going to ask “I have telescope time right now, which of my follow-up objects should I observe next?”. The second new thing is that I think that it is insufficient to make this decision only on the basis of information obtained in this observation. It should be made based on the future discounted information that it unlocks or makes available, under assumptions about observing into the future.

This second point was a breakthrough for me. It comes from this point: Imagine that you are using RV measurements to measure precise periods, and you want period information. The first observation you make gives you no period information whatsoever: It only constrains the overall system velocity! So you would never make that first observation if you cared only about the immediate information gain on period. You have to think about the future information-gain potential that your observation unlocks, discounted by your discount rate. Or even more complex objectives (yes, cash flow ought to be involved).

In other news, Guy Davies (Birmingham) made a nice point in discussion of the time-domain behavior of stars in an open cluster observed by Kepler: Because these stars ought to be the same age, and the same composition, and (on the red-giant branch) nearly the same mass, the asteroseismological (and jitter) signals ought to—in some sense—lie along a one-dimensional sequence in the relevant space. That's a great idea; I want to test that.